Toning photographic material



Dec. 30, 1941.

G. P, HAM 2,268,508

TONING PHOTOGRAPHIC MATERIAL File@ Dec. s, '1959 FIG` f.

70o my POTH S/UM FFPR/ /V/DE Patented Dec. 30, 1941 UNITED STATES PATENT OFFICE TONIN G PHOTOGRAPHIC MATERIAL Garnet Philip Ham, Old Greenwich, Conn., as-

signor to American Cyanamld Company, New York; N. Y., a. corporation of Maine Application December 8, 1939, Serial No. 308,108

8 Claims.

This invention relates to the toning of photographic material by means vof ferricyanides. Potassium ferricyanide has been used as a toning medium for photographic material to obtain blue e colored which detracts from the brilliance, particularly when the material is to be projected which is one of the most important uses for toning photographic material.

Another factor in the projection of blue toned photographic material is the color. The blue obtained with potassium ferricyanide is more nearly a pure blue showing a little if' any drop in transmission in the violet. The rst objection to the potassium ferricyanide toned material is y applicable both to blue and red brown tones, the

color characteristic however is noted only in the blue.

The present invention utilizes two diierent ferricyanides which are characterized by the fact that they are either monosodium diamidine or monosodium dipotassium lerricyanides. These mixed ferricyanides containing one equivalent of sodium and two equivalents of either potassium or an amidine such as guanidlne, are characterized by two important properties.

When they are used as a constituent of a toning bath with blue or red brown, they produce clear and brilliant highlights particularly on proiection. They also possess the very important property that when used in blue toning solutions an entirely different color oi' blue is produced which is greenish blue.

'I'he color differences are illustrated in the' drawing in which:

Fig. 1 is a series of three spectrophotometric curves of a blue tone lantern slide;

Fig. 2 is a set of corresponding spectrophotoamination oi the figure of the drawing would indicate that the blue obtained with potassium ierricyanide would be ideal and-that the blues obtained with mono-sodium diguanidine or mono-sodium dipotassium ferricyanides are not as satisfactory as their transmission in the violet falls o very greatly. However, an ideal blue grade presupposes several other factors. First, it presupposes that the other subtractive colors in the three other images are perfectly balanced.

This is not true as frequently the magenta is too high in violet and requires compensation which can be eected by a blue image with a lower violet transmission. The net color effect appears more pleasing and more natural to the eye, particularly when projected with ordinary incandescent tungsten light deficient in violet.

A diierent form of color combination was possible in the past by using mixtures of other dyes but hlthereto was not possible with a single iron blue toning pigment which is much cheaper and has many advantages such as light fastness and the like. Accordingly the blue toned images producible by the present invention make color corrections possible with cheap and economical dyes of color.

The' spectrophotometric curves of the gures were made with a special spectrophotometer drive which draws a curve proportional to the log log reciprocal of the transmission such as is described in the patent to Pineo U. S. 2,176,013, issued October 10, 1939. Curves drawn by such a machine have an important advantage that their shape is not aiected by variations in concentration but is a true indication of the relative color. Such a curve requires a special scale for reading.

It is an advantage of the present invention that it is applicable to the standard formulae for toning and does not require any departure from standard procedures apart from the use of the monosodium diamidine or dipotassium ferricyanide.

The invention will be described in greater detail in conjunction with the following examples:

` Example 1 A solution of the following composition was prepared:

' Water ml--- 1000.00 Diguanidine sodium ferricyanide g 23.00 Potassium 'bromide g-- 5.00

This solution was used to bleach a standard glass lantern slide positive. Bleaching was effected at 23 C. for five minutes. The lantern slide was then washed thoroughly in Water and toned blue by means of the following solution:

Ammonium persulfate g 0.50 Iron and ammonium sulfate g-- 1.40 Oxalic acid g 3.00 Diguanidine sodium ferricyanide g 1.15 Ammonium alum g-- 5.00 Hydrochloric acid (10%) ml 1.00 Water y-m1-- 1000.00

for live minutes at 25 C. Thereupon the lantern slide was washed with water for three minutes and dried. Brilliant highlights resulted and the blue had a distinct greenish shade. A spectrophotometric curve of the material is shown in the drawing.

Example 2 The procedure of Example l was followed but instead oi diguanidine sodium ferricyanide, sodium dipotassium ferricyanide was substituted.

`The result was a lantern slide with the same brilliant highlights and a similar greenish-blue color. The spectrophotometric curve likewise appears 'in the drawing.

Example 3 for iive minutes at 25 C.. Then it was washed with water for 3 minutes and dried. The result was a slide of excellent clear highlights with no tendency for the shadows to be blocked up or for any lack of clarity. The slide projected to form a brilliant image as do slides of Examples 1 and 2. A'Ioned slides oi the presentexample however show a clear brown while the transmission in the violet and the extreme red-is substantially the same, a 'higher transmission is shown in the blue green, green, and yellow than is the case with the corresponding slide toned with potassium erricyanide.

Ellample 4 The procedure of Example 3 was followed but instead of sodium diguanidine ferricyanide, sodiurn dipotassium ferricyanide was used. Again a slide with brilliant highlights was obtained, the color being substantially the same as in the previous example. Spectrophotometric curves of the slides from the last two examples compared with the one toned as in Fig. 2 of the drawing.

In the examples, a typical amidine ferricyanide, namely the sodium diguanidine ferricyanide, is described. Other sodium diamidine ferricyanides can be used in which the amidine contains the guanyl radical. 'I'he preliminary bleaching the blue toning of Examples 1 and 2 is described as being eected with sodium diguanidine ferricyanide. It is not necessary to use the sodium amidine ierricyanide for this preliminary bleach-u ing step and potassium ferricyanicle can be used without materially aiiecting the iinal color. However, it is advantageous to use either sodium diguanidine erricyanide or sodium dipotassium ferricyanide in the bleaching step because any of the chemical which may not have been completely washed out and hence will be present in the toning step will correspond to the ferricyanide used in. the last step and will not tend topioduce any of the sh'ade which is normally produced in potassium ferricyanide toning.

Whatl claim is:

1. A method of toning photographic material having a metallic silver image thereon which comprises subjecting the material to the action of toning baths included in the group consisting decanos of sodium diaminoamidne erricyanide. the molar ratio of aminoamidine to ierricyanide being 2:1 and toning baths containing eective amounts of sodium dipotassium ferricyanide in which the molar ratio of potassium to ferricyanide is 2:1, the bath' also containing at least one metal salt capable of reacting with the reaction product of the metallic silver image and the ferricyanide to yield a colored water insoluble iron cyanogen complex of the metal.

2. A method of toning photographic material having a metallic silver image blue which cornprises bleaching the image and subjecting the bleached material to the action of a toning bath containing a ferric salt and an eiective amount of a ferricyanide included in the group consisting of sodium diaminoamidne ferricyanide, the molar ratio of diaminoamidine to erricyanide being 2:1 and sodium dipotassium ierricyanide, th'e molar ratio of potassium to ferricyanide being 2:1,

3. A method of tonim3f photographic material having a metallic silver image red brown which comprises bleaching the image and subjecting the bleached materiai to the action of a toning bath containing a uranium salt and an eiective amount of a ferricyanide included in the group consisting oi' sodium diaminoamidine ferricyanide, the molar ratio of diaminoamidine to ferricyanide being 2:1 and sodium dipotassium ferricyanide, the molar ratio of potassium to ferri cyanide being 2:1.

of toning baths containing an edective amount 4. A. method of toning photographic material having a metallic silver image which' comprises subjecting the material to the `action of toning baths containing an effective amount of sodium diguanidine ferricyanamide, the molar ratio of guanldine to ferricyanide being 2:1, and a metal salt capable of reacting with the reaction product of the imageand the sodium diguanidine ferricyanide to produce a colored insoluble complex of the metal and the ferricyanide.

5. A method of toning blue photographic material having a silver image which comprises bleaching the image and subjecting the bleached materia-l to the action of a toning bath con-taining a ferrie salt and eiective amounts of sodium diguanidine ferricyanide, the molar ratio of guanidine to ferricyanide being 2:1.

6. A method oi' toning photographic material having a metallic silver image which comprises subjecting the material to the action of toning baths containing an eiective amount of sodium dipotassium ferricyanide, the molar ratio of potassium to ferricyanide being 2:l, and a metal salt capable of reacting with the reaction product of the image and the sodium dipotassium ferricyanide to produce a colored insoluble complex of the metal and the ferrlcyanide.

7. A method of toning blue photographic material having a silver image which comprises bleaching the image and subjecting the bleached material to the action of a toning bath containing a ierric salt and effective amounts of sodium dipotassium ferricyanide, the molar ratio ci' potassium to ierrlcyanidebeing 2 1.

8. A method of toning red-brown photographic material having a metallic silver image which comprises subjecting the material to the action of a toning bath containing a uranium salt and an eiective amount of sodium dipotassium ferricyanide, the molar ratio of potassium to ferricyanide being 2 1.

GARNET PHILIP HAM. 

